All electronics devices consume power. The power consumed translates directly into cost for an end user. For example, the power consumed by a home video cassette recorder results in an energy bill. For mobile devices the power consumed also translates into a certain time for which a device will operate. For example, when a portable audio player runs on batteries. In general saving power is always of benefit to an end user. This can be achieved by operating devices as efficiently as possible. This is true for both situations in the home and on the move.
In U.S. Pat. No. 6,167,524 an apparatus and method is disclosed for controlling power consumption in portable personal computers by dynamically allocating power to the system logic. Expected total power consumption is calculated and compared to an optimum power efficiency value. The expected power consumption values for each execution unit are stored in a look-up table in actual or compressed form. If the expected total power consumption value exceeds the power efficiency value, selected execution units are made inactive. This may also include cancelling operations, most notably speculative operations. Conversely, if the power efficiency value exceeds the expected total power consumption value, execution units functions are added in order to maintain a level current demand on the battery.
Electronic devices operating in the Consumer Electronics domain generally have requirements of providing a guaranteed quality of service to an end user. For example, an audio playback device should always play the audio desired by an end user and a video playback device should always play the video desired by an end user and this should be performed without noticeable glitches in the audio or video playback. Furthermore, in such Consumer Electronics devices there are generally multiple units for processing the data beyond the execution units that consume significant amounts of power. For example, storage units, such as hard disk drives or optical drives, or communications units, such as a network controller or WiFi interface, consume significant power. Therefore, a solution that is not specific for execution units would be preferable. Additionally, the use of speculative operations is uncommon in Consumer Electronics devices therefore the cancelling of speculative operations is less applicable. Even without the use of speculative operations the cancelling of operations in general is not possible in Consumer Electronics devices, since this will likely impact upon the quality of service delivered.
The inventors recognising this problem devised the present invention.